scholarly journals Status and Trends of the Lake Ontario Macrobenthos

1991 ◽  
Vol 48 (8) ◽  
pp. 1558-1567 ◽  
Author(s):  
Thomas F. Nalepa
Keyword(s):  
Great Lakes ◽  
River Mouth ◽  
Lake Ontario ◽  
The Other ◽  
Niagara River ◽  
Major River ◽  
Trends Over Time ◽  
The 1960S ◽  
River Mouths ◽  
The Impact

The benthic macroinvertebrate community of Lake Ontario was examined relative to communities found in the other Great Lakes and also relative to trends over time. In the nearshore, populations are heavily influenced by municipal and industrial inputs. For example, oligochaete abundances in the nearshore are higher than in any of the other Great Lakes (excluding shallow Lake Erie), communities have been altered even to relatively deep depths near the major river mouths, and the pollution-sensitive Pontoporeia hoyi is scarce along the southern shoreline east of the Niagara River mouth. In the profundal, benthic composition is similar to that found in the other Great Lakes, but biomass is less than might be expected given the amount of organic material settling to the bottom. Benthic standing stocks in this region have apparently declined almost threefold since the 1960s. Reasons for this decline do not appear to be related to trends in water column productivity or to predation pressure, but may be related to the accumulation of contaminants. Research needs include studies to assess benthic trends over a much broader area of the lake and studies to examine the impact of sublethal levels of contaminants.

scholarly journals Climatic-change implications from long-term (1823-1994) ice records for the Laurentian Great Lakes

1995 ◽  
Vol 21 ◽  
pp. 383-386 ◽  
Author(s):  
R.A. Assel ◽  
D.M. Robertson ◽  
M.H. Hoff ◽  
J.H. Selgeby
Keyword(s):  
Great Lakes ◽  
Climatic Changes ◽  
The Other ◽  
Laurentian Great Lakes ◽  
Great Lakes Region ◽  
Lake Mendota ◽  
Air Temperatures ◽  
The 1960S ◽  
Different Parts

Long-term ice records (1823-1994) from six sites in different parts of the Laurentian Great Lakes region were used to show the type and general timing of climatic changes throughout the region. The general timing of both freeze-up and ice loss varies and is driven by local air temperatures, adjacent water bodies and mixing, and site morphometry. Grand Traverse Bay and Buffalo Harbor represent deeper-water environments affected by mixing of off-shore waters; Chequamegon Bay, Menominee, Lake Mendota, and Toronto Harbor represent relatively shallow-water, protected environments. Freeze-up dates gradually became later and ice-loss dates gradually earlier from the start of records to the 1890s in both environments, marking the end of the “Little lce Age”. After this, freeze-up dates remained relatively constant, suggesting little change in early-winter air temperatures during the 20th century. Ice-loss dates at Grand Traverse Bay and Baffalo Harbor but not at the other sites became earlier during the 1940s and 1970s and became later during the 1960s. The global warming of the 1980s was marked by a trend toward earlier ice-loss dates in both environments.

scholarly journals Sand Bypassing Methodology For Sustainable River Mouth Opening

2019 ◽  
Vol 8 (2S11) ◽  
pp. 2280-2284
Keyword(s):  
Sediment Transport ◽  
Tamil Nadu ◽  
Mouth Opening ◽  
River Mouth ◽  
The Other ◽  
Natural Sediment ◽  
Water Level Rise ◽  
Model Study ◽  
River Training ◽  
The Impact

River inlets along the Tamil Nadu coast remain mostly closed due to negligible fresh water flow and also due to various structures constructed near to the river inlet obstructing natural sediment transport. Excessive development of the sand spit also causes serious problems such as water level rise during floods and difficulty in navigation through river mouth. To reduce the impact of coastal area flooding and easy navigation it is necessary to keep the river mouth open. River training walls (RTW) are generally constructed to keep the river mouth open. Depending upon the sediment transport direction, sediments get deposited on one side of the RTW, while depleting the sediments from the other side. To prevent the sediment deposit from spilling over to river mouth, it is ideal to bypass the sand to the other side of the river mouth. This study analyses the methodologies for sand bypassing. A numerical model study has been carried out using DHI LITPACK to evaluate the sedimentation. The procedure of sand bypassing using pumps and pipe lines are discussed. Volume of sand bypassed, pump capacity, the number of Booster pumps to maintain critical velocity etc. can be determined based on the procedure discussed

Hydrological Risk Phenomena and Flood Analysis

2015 ◽  
pp. 284-311
Author(s):  
Constantin Buta ◽  
Ichinur Omer ◽  
Andreea Andronic
Keyword(s):  
Black Sea ◽  
The Other ◽  
The Black Sea ◽  
Theoretical Concepts ◽  
River Catchment ◽  
Catchment Size ◽  
Major River ◽  
Flood Analysis ◽  
The One ◽  
The Impact

This paper is one detailed research of the major river basins of the Romanian North Dobrogea, Taita River Catchment. The Taita River has a catchment size of about 591 km 2 and is flowing into the Black Sea through Topraichioi Lake after 57 km. Upstream it has an elevation about 240 m height and 0 m at downstream (the reference is the Black Sea). The complexity of this research study is given, on the one hand, by the descriptive side of the natural aspects (geological, morphological, climatic aspects, hydrology and the soil) and, on the other hand, by the practical side, boosted by the information system processing of data. This study presents the theoretical concepts concerning the hazards and the risk, which, for a better interpretation of the impact of these phenomena, are supplemented by the maps, graphs and photographs.

Sediment records of the influence of river damming on the dynamics of the Nelson and Churchill Rivers, western Hudson Bay, Canada, during the last centuries

The Holocene ◽  
2016 ◽  
Vol 27 (5) ◽  
pp. 712-725 ◽  
Author(s):  
Quentin Duboc ◽  
Guillaume St-Onge ◽  
Patrick Lajeunesse
Keyword(s):  
River Mouth ◽  
Sediment Concentration ◽  
Hudson Bay ◽  
Continuous Control ◽  
Dam Construction ◽  
Physical Chemical ◽  
Hyperpycnal Flows ◽  
Western Hudson Bay ◽  
The 1960S ◽  
The Impact

Two gravity cores (778 and 780) sampled at the Nelson River mouth and one (776) at the Churchill River mouth in western Hudson Bay, Canada, were analyzed in order to identify the impact of dam construction on hydrology and sedimentary regime of both rivers. Another core (772) was sampled offshore and used as a reference core without a direct river influence. Core chronology was established using 14C and 210Pb measurements. Cores 778 and 780 show greater variability than the others, and the physical, chemical, magnetic, and sedimentological properties measured on these cores reveal the presence of several hyperpycnites, indicating the occurrence of hyperpycnal flows associated with floods of the Nelson River. These hyperpycnal flows were probably caused by ice-jam formation, which can increase both the flow and the sediment concentration following the breaching of such natural dams. However, these hyperpycnites are only observed in the lower parts of cores 778 and 780. It was not possible to establish a precise chronology because of the remobilization of sediments by the floods. Nevertheless, some modern 14C ages suggest that this change in sedimentary regime is recent and could be concurrent with the dam construction on the Nelson River, which allows a continuous control of its flow since the 1960s. This control prevented the formation of hyperpycnal flows and the deposition of hyperpycnites. Finally, core 776 contains only one rapidly deposited layer. This lower frequency may be related to the enclosed estuary of the Churchill River, its weaker discharge, and the distance of the site from shore.

Rehabilitation of Lake Ontario: the Role of Nutrient Reduction and Food Web Dynamics

1991 ◽  
Vol 48 (8) ◽  
pp. 1574-1580 ◽  
Author(s):  
John H. Hartig ◽  
James F. Kitchell ◽  
Donald Scavia ◽  
Stephen B. Brandt
Keyword(s):  
Water Quality ◽  
Great Lakes ◽  
Food Web ◽  
Toxic Substance ◽  
Lake Ontario ◽  
The United States ◽  
Food Web Dynamics ◽  
Food Web Interactions ◽  
The Impact

The Laurentian Great Lakes have a complex history of changes due to eutrophication, invasion of exotic species, and fisheries and phosphorus management practices. Remedial actions have reduced nutrient loadings and enhanced the role of food web interactions in improving water quality. Workshops sponsored through the United States – Canada international Joint Commission have addressed the relative importance of nutrient abatement and/or food web manipulation in affecting water quality trends. Both controls have combined to enhance water clarity in Lake Michigan. Lake Ontario has already exhibited the effects of nutrient controls and may be on the verge of manifesting food web controls. Research and monitoring recommendations to elucidate the effects of nutrient and food web controls include the following: (1) water quality and fisheries agencies must coordinate monitoring activities, standardize techniques, and establish and maintain long-term data sets to evaluate the effects of water quality and fisheries programs separately and together; (2) controlled, mesoscale, whole-system experiments should be performed to quantify rates (e.g. growth, predation, etc.) of food web interactions; and (3) the scientific community should promote research which quantifies the impact of changes in food web dynamics on changes in toxic substance levels in Great Lakes fishes.

Distribution of Chlorobenzenes, Pesticides and PCB Congeners in Lake Ontario Near the Toronto Waterfront

1992 ◽  
Vol 27 (4) ◽  
pp. 751-772 ◽  
Author(s):  
Efraim Halfon ◽  
Don Poulton
Keyword(s):  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Lake Ontario ◽  
Lake Levels ◽  
Niagara River ◽  
Pcb Congeners ◽  
Sources Of Pollution ◽  
Local Sources ◽  
The Impact

Abstract Concentrations of 89 toxic organic pollutants (25 contaminants, including chlorobenzenes and pesticides, and 64 PCB isomers) were measured in Lake Ontario along the Toronto Waterfront area during the spring, summer and fall of 1987. Data indicate that Humber Bay, the inner harbour, and the areas near the Toronto Main Sewage Treatment Plant (STP) are the most polluted. While contaminant levels in some offshore areas are high, average levels for most contaminants are similar to whole-lake levels. Lake Ontario receives large amounts of pollutants from atmospheric sources and the Niagara River. Consequently, the impact of both local and whole-lake sources is felt in the Toronto Waterfront Area. Thus, even if all local sources of pollution were removed, the Toronto Waterfront Area would probably remain affected by other sources, primarily the Niagara River. Concentrations of toxic pollutants would remain approximately the same as far as two kilometers from shore.

Mixing Characteristics of the Niagara River Plume in Lake Ontario

1989 ◽  
Vol 24 (1) ◽  
pp. 143-162 ◽  
Author(s):  
C. R. Murthy ◽  
K. C. Miners
Keyword(s):  
General Circulation ◽  
River Mouth ◽  
Lake Ontario ◽  
Intermediate Stage ◽  
River Plume ◽  
Thermal Front ◽  
Niagara River ◽  
Initial Stage ◽  
Mixing Characteristics ◽  
Lagrangian Drifter

Abstract Data collected between 1982 and 1985 from Lagrangian drifter experiments in which about ten drifters were tracked for ten to twelve hours from their release across the Niagara River mouth, and from concurrently taken ship-based temperature soundings at fixed grid stations off the river mouth, are used to develop a conceptual model of the mixing characteristics of the Niagara River in Lake Ontario. The data obtained suggest a three-stage mixing process. In the initial stage, the river inflow momentum dominates and the plume is well mixed vertically. In the intermediate stage, the interaction of the well mixed, buoyant river plume with colder water from deeper depths of the lake generates a sharp thermal front. In the final stage, the river plume responds to the prevailing winds and the general circulation of the lake. The correlation between these observed plume characteristics and the distribution of toxic contaminants such as mercury and mirex in Lake Ontario sediments attributed to Niagara River outflow is illustrated.

scholarly journals Climatic-change implications from long-term (1823-1994) ice records for the Laurentian Great Lakes

1995 ◽  
Vol 21 ◽  
pp. 383-386 ◽  
Author(s):  
R.A. Assel ◽  
D.M. Robertson ◽  
M.H. Hoff ◽  
J.H. Selgeby
Keyword(s):  
Great Lakes ◽  
Climatic Changes ◽  
The Other ◽  
Laurentian Great Lakes ◽  
Great Lakes Region ◽  
Lake Mendota ◽  
Air Temperatures ◽  
The 1960S ◽  
Different Parts

Long-term ice records (1823-1994) from six sites in different parts of the Laurentian Great Lakes region were used to show the type and general timing of climatic changes throughout the region. The general timing of both freeze-up and ice loss varies and is driven by local air temperatures, adjacent water bodies and mixing, and site morphometry. Grand Traverse Bay and Buffalo Harbor represent deeper-water environments affected by mixing of off-shore waters; Chequamegon Bay, Menominee, Lake Mendota, and Toronto Harbor represent relatively shallow-water, protected environments. Freeze-up dates gradually became later and ice-loss dates gradually earlier from the start of records to the 1890s in both environments, marking the end of the “Little lce Age”. After this, freeze-up dates remained relatively constant, suggesting little change in early-winter air temperatures during the 20th century. Ice-loss dates at Grand Traverse Bay and Baffalo Harbor but not at the other sites became earlier during the 1940s and 1970s and became later during the 1960s. The global warming of the 1980s was marked by a trend toward earlier ice-loss dates in both environments.

Changes in the Fish Species Composition of the Great Lakes

1974 ◽  
Vol 31 (5) ◽  
pp. 827-854 ◽  
Author(s):  
W. J. Christie
Keyword(s):  
Great Lakes ◽  
Exotic Species ◽  
Lake Trout ◽  
Lake Ontario ◽  
Sea Lamprey ◽  
Turn Of The Century ◽  
The Other ◽  
Pest Species ◽  
Rainbow Smelt ◽  
Fish Species Composition

This paper is an interpretive review of the "case histories" which documented the changes in each of the Laurentian Great Lakes for the 1971 symposium on Salmonid Communities in Oligotrophic Lakes (SCOL). It suggests that lakes Huron, Michigan, and Superior passed through a parallel series of stock changes after the invasions of those lakes by the sea lamprey. First, the lake trout and burbot stocks collapsed, and then with the relaxation of predation pressure rainbow smelt, deepwater cisco, and alewife stocks increased. Lake herring stocks collapsed in apparent response to the smelt increase. Whitefish were affected by sea lamprey but recovery after the control of the lamprey in lakes Michigan and Superior suggested that the exotic species had little influence. Lake Ontario differed from the other lakes in that it was inhabited by both sea lamprey and alewife before the turn of the century, and provided the reservoir from which these species expanded to colonize the upper lakes. Alewife apparently equilibrated early, but the evidence was that more recent perturbations allowed the sea lamprey to become a significant factor in the loss of the piscivores of Lake Ontario. Subsequent proliferation of ciscoes and smelt, and collapse of the herring, followed a sequence similar to that of the upper lakes. Lake Erie seemed to be similarly affected by loss of predator stocks, but its predominantly eutrophic character made the situation more complex. Overfishing was indicted in many early stock collapses, in the early invasion of the smelt in lakes Huron and Michigan and in the recent cisco declines of lakes Ontario and Huron. Eutrophication and more direct pollution stresses had mainly inshore impacts, but the similarity in the species sequencing in the oligotrophic Great Lakes suggested that although these factors may have supplemented the other effects, their influence before about 1950 was less than that of overfishing and the invasion of exotic species. Control of sea lamprey, overfishing, and eutrophication seemed attainable in the Great Lakes, but the only defense against further invasions by pest species appeared to be maintenance of sufficiently dense piscivore stocks to assure their suppression. Determining the levels of harvest appropriate to this provision will require intensified research.

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